Examining the association between short interpregnancy interval births and the type and timing of postpartum long acting reversible contraception

Objective: To determine whether the type (intrauterine device or implant) or timing (immediately postpartum vs interval) of postpartum long-acting reversible contraception was associated with a reduction in short interpregnancy interval births. Study Design: We conducted a retrospective cohort study using linked Medicaid claims and birth certificate data from Oregon and South Carolina, 2010 to 2018. Our primary outcome was short interpregnancy interval, defined as repeat pregnancy within 18 months of the index delivery. We determined postpartum contraceptive method and timing of receipt. To assess the association of timing of long acting reversible contraception with short interpregnancy interval, we calculated adjusted probabilities from a logistic regression model incorporating covariate balanced propensity score weights, sociodemographic factors, and clustered at the woman-level. Results: Our study sample included 121,422 births to 97,084 individuals who had more than 1 birth during the study period; 41% had a short interpregnancy interval. A majority of individuals had not received any contraception by 6 months postpartum (68.6%). Overall, 15,477 individuals used long acting reversible contraception postpartum, with the majority receiving interval rather than immediate postpartum long acting reversible contraception (92.9% vs 7.1%). In multivariable analyses, both immediate postpartum (23.0%, 95% CI: 20.5%–25.8%) and interval long acting reversible contraception (15.2%, 95% CI: 14.4%–16.1%) are associated with a lower probability of short interpregnancy interval than short acting methods (42.1%, 95% CI: 41.2%–43.0%). Conclusion: Compared to short-acting methods, receipt of both immediate postpartum and interval long-acting reversible contraception is associated with lower probabilities of a subsequent short interpregnancy interval. Implications: All long acting, reversible contraception, whether placed immediately postpartum or on an interval basis, was associated with a significantly lower probability of a short interpregnancy interval than short acting or no contraceptive method.